The Optical Biology Shared Resource (Opticore) provides access to state-of-the-art flow cytometry, cell sorting, and laser scanning cytometry for the UC Davis Cancer Center community. The core facility is located on the Davis campus with two satellites in Sacramento. The objectives of this shared resource are to: provide state-of-the-art cell sorting and analytical cytometry; provide consultation about appropriate experimental design and data analysis; provide education about routine as well as cutting-edge cytometry applications; facilitate interactions among researchers using these techniques; and stimulate development of new approaches for cancer research. This shared resource provides cost-effective services and training. Investigators and their laboratory members work closely with the Technical Director to learn to use multicolor benchtop analyzers. The staff teaches an annual summer flow cytometry course for new users. Multi-laser, high-speed cell sorters are available on both campuses and are operated by Opticore staff. A biohazard containment system permits sorting of unfixed cells. The 3-laser scanning cytometer is configured for multiparameter and high-throughput applications, including analysis of tissue microarrays. These instruments have been upgraded with institutional support and are maintained through ongoing service contracts. The Cancer Center administration has designed and implemented a web-based reservation and reporting system. Dr. Barbara Shacklett is the Scientific Director; the Technical Director, Ms. Oxford, has developed notable expertise in multicolor analysis and high speed sorting. She is assisted by a Technical Manager, Ms. McLaughlin, who supervises operations in Sacramento. An Advisory Committee meets at least once a year to review operations, set policy, and make plans. Since the last submission, the user pool has expanded and Cancer Center members from all six research programs have used this shared resource. Members currently account for over 80% of its use, generating results published in high-impact journals and submitted in grant applications.